1. Technical Field of the Invention
The present invention relates in general to optical MEMS, and in particular, to optical scanner architectures using MEME.
2. Description of Related Art
Micro Electro-Mechanical Systems (MEMS) refers to the integration of mechanical elements, sensors, actuators and electronics on a common silicon substrate through microfabrication technology. For example, the microelectronics are typically fabricated using an integrated circuit (IC) process, while the micromechanical components are fabricated using compatible micromachining processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical components. MEMS devices are attractive candidates for use in spectroscopy, profilometry, environmental sensing, refractive index measurements (or material recognition), as well as several other sensor applications, due to their low cost, batch processing ability and compatibility with standard microelectronics. In addition, the small size of MEMS devices enables the integration of equipment incorporating MEMS devices into mobile and hand held devices.
Moreover, MEMS technology, with its numerous actuation techniques, enables the realization of new functions and features of photonic devices, such as optical tunability and dynamic sensing applications. Optical scanners are important elements for many industrial applications such as bar code readers, laser scanning in free space, optical communication and surveillance, laser radar, optical coherence tomography and imaging. The fabrication of optical scanners using MEMS technology allows their use in new and innovative applications, such as endoscopes, optical microscopes and various applications that require portability and mobility. In additional to the intrinsic advantages offered by the MEMS technology, such as small size, low fabrication cost due to batch processing and low power consumption, MEMS microscanners can also be easily integrated in a complete system, even with a laser source in the same package.
Therefore, intensive industrial and academic research has been oriented in the last decade towards the fabrication of 1-D and 2-D optical microscanners using MEMS technology. The bulk of this research has been based on the use of rotating micromirrors, where the mirror is built in either the substrate plane using surface micromaching technology or in the plane normal to the substrate using DRIE (Deep Reactive Ion Etching) in SOI technology. Different actuation forces have also been suggested, such as utilizing electrothermal force through structure bending or electrostatic force through a comb drive actuator.
Researchers are now focusing their attention on producing a micromirror with a wide rotation angle. However, except when using special materials, such as polyamides or magnetic materials that are not common in microelectronics technology, where the rotation angles can achieve wide values (i.e., 45 or 50 degrees), most of the structures based on rotating mirrors are limited to rotation angles in the order of ±10 degrees.